Predictive Utility of UPDRS for Peak Aerobic Capacity and Ambulatory Function

1. The Unified Parkinson’s Disease Rating Scale as a predictor of peak aerobic capacity and ambulatory function Frederick M. Ivey, PhD; Leslie I. Katzel, MD, PhD; John D. Sorkin, MD, PhD; Richard F. Macko, MD; Lisa M. Shulman, MD

2. Aim • Assess utility of Unified Parkinson’s Disease Rating Scale (UPDRS) for predicting peak aerobic capacity (VO2 peak) and ambulatory function. • Relevance • UPDRS is widely applied disease severity index but doesn’t assess cardiovascular fitness and provides only limited information on functional performance. • Therefore, there is value in determining predictive power of UPDRS for more time-consuming and resource-intensive measures such as VO2 peak and ambulatory function.

3. Method • 70 participants were evaluated: • UPDRS (Total and Motor ratings). • VO2 peak. • 6-minute walk distance (6MW). • 30-foot self-selected walking speed (SSWS). • We determined how well Total and Motor UPDRS scores predicted each functional capacity measure. • We also tested whether adding Hoehn & Yahr scale (H-Y) changed UPDRS’s predictive power.

4. Results • Adjusted for age and sex, both Total and Motor UPDRS subscales failed to predict VO2 peak. • Total UPDRS weakly predicted 6MW and SSWS (p < 0.05) • Motor UPDRS subscale didn’t predict these ambulatory function tests. • After adding H-Y to model, Total UPDRS was no longer independent predictor of 6MW but remained predictor of SSWS.

5. Relationship between total UPDRS and (a) 6MW or (b) SSWS. Modest but significant relationship disappeared after adding Hoehn and Yahr to model for (a) but not (b).

6. Conclusion • Total and Motor UPDRS rating scales do not predict VO2 peak • But weak relationship exists between Total UPDRS and measures of ambulatory function.